Underground drilling involves drilling a bore through a formation deep in the Earth using a drill bit connected to a drill string. Two common drilling methods, often used within the same hole, include rotary drilling and slide drilling. Rotary drilling typically includes rotating the drilling string, including the drill bit at the end of the drill string, and driving it forward through subterranean formations. This rotation often occurs via a top drive or other rotary drive means at the surface, and as such, the entire drill string rotates to drive the bit. This is often used during straight runs, where the objective is to advance the bit in a substantially straight direction through the formation.
During rotary drilling, the rotational force applied at the top drive is often out of phase with the reaction at the bottom-hole assembly (BHA) of the drill string due to an elasticity of the material of the drill string, causing the drill string to yield somewhat under the opposing loads imposed by the rotational force at the top drive and friction/inertia at the end where the bit is located. This causes resonant motion to occur between the top drive and the BHA that is undesirable. Further, as the drill string winds up along its length due to the ends being out of phase, the force stored in the winding may exceed any static friction, causing the drill string near the bit to slip relative to the wellbore sides at a high (and often damaging) speed. Measured torque of the drill string may be used in addition to other techniques to adjust a rotation speed during the rotary drilling to reduce the chance of stick-slip and/or other vibrations.
Directional drilling can be accomplished using slide drilling. Slide drilling is often used to steer the drill bit to effect a turn in the drilling path. For example, slide drilling may employ a drilling motor with a bent housing incorporated into the BHA. During typical slide drilling, the drill string is not rotated and the drill bit is rotated exclusively by the drilling motor. The bent housing steers the drill bit in the desired direction as the drill string slides through the bore, thereby effectuating directional drilling. Alternatively, when no directional change is desired, the steerable system can be operated in a rotating mode in which the drill string is rotated while the drilling motor is running.
To reduce wellbore friction during slide drilling, a top drive may be used to oscillate or rotationally rock the drill string during slide drilling to reduce drag of the drill string in the wellbore. This oscillation can reduce friction (e.g., by converting static friction on sections of the drill string to dynamic friction, which has a lower coefficient) in the borehole.
However, some systems that oscillate the drill string during slide drilling do so without knowledge of the resonant motion (e.g., a torsional wave traveling along the length of the drill string) at the top drive. Without knowledge of the resonant motion, drilling operators may under-utilize the oscillation feature while slide drilling due to concern about inadvertently changing the toolface orientation of the bottom hold assembly. This results in less efficient drilling and/or less bit progression due to greater static friction forces acting on the drill string. In addition, current systems do not use resonant motion to control toolface orientation to either maintain a desired toolface orientation or to change the orientation of toolface orientation to a desired orientation while drilling. The present disclosure addresses one or more of the problems of the prior art.